Hitherto, in a refrigerant compressor used in vapor compression-type refrigeration cycle devices (such as heat pump equipment and refrigeration cycle equipment), a rotational force of an electric motor is transmitted to a compression mechanism by a drive shaft so that refrigerant gas is compressed. In such a refrigerant compressor, the refrigerant gas compressed by the compression mechanism is discharged into a hermetic container, moved from a space below the electric motor into a space above the same through electric motor unit gas passages, and then discharged into a refrigerant circuit on an outside of the hermetic container. At this time, lubricating oil supplied to the compression mechanism and mixed with the refrigerant gas is discharged to the outside of the hermetic container. Hitherto, there is a problem in that an increase in amount of the oil to be discharged into the refrigerant circuit causes degradation in performance of a heat exchanger. In addition, there is another problem in that a decrease in amount of the oil stored in the hermetic container causes insufficient lubrication, resulting in degradation in reliability of the refrigerant compressor.
In recent years, there have been promoted development of refrigerant compressors having smaller sizes, and conversion to use of alternative refrigerants (including natural refrigerant) having a lower environmental load. Under the circumstances, advanced technology for separating the oil in the hermetic container has been demanded. However, how the refrigerant and the lubricating oil flow and how the oil separation occurs during high speed rotation of the electric motor in the hermetic container are significantly complicated, and observation experiments in the hermetic container under high pressure are not easy. Thus, there are a large number of unknown factors, and a large number of technical problems have not yet been solved.
In the high-pressure shell type scroll compressor disclosed in Patent Literature 1, sucked refrigerant is compressed by the compression mechanism arranged on an upper side in the hermetic container, and once caused to flow down to an oil reservoir at a bottom of the hermetic container. After that, the refrigerant is caused to flow up from a space below the electric motor to a space above the same through electric motor gas passages, and then discharged as high pressure gas through a discharge pipe of the compressor. The high-pressure shell type scroll compressor disclosed in Patent Literature 1 includes a fan arranged on an upper portion of a rotator of the electric motor, and partition walls for separating a stator side of the electric motor and a rotator side of the electric motor from each other above the fan. Then, the refrigerant and the lubricating oil are separated from each other by using a centrifugal force generated by rotation of the fan and by using pressure resistance generated through gaps between the partition walls. The lubricating oil is prevented from flowing directly into the discharge pipe without being separated from the refrigerant, in other words, the lubricating oil is prevented from flowing out from the hermetic container.
Further, in Patent Literature 2, there is disclosed an oil separation device for a hermetic electric compressor including: an electric component housed in an upper portion of a hermetic container; a compression component that is driven by the electric component; an oil separation plate arranged to face an upper end ring of a rotor of the electric component across a predetermined clearance; and stirring vanes arranged upright to the oil separation plate, in which the stirring vanes are arranged upright only to a lower surface of the oil separation plate.
Effects of improving an oil separation condition in the hermetic container of the compressor by using the fan and the partition walls in Patent Literature 1 and the oil separation plate and the stirring vanes in Patent Literature 2 are generally observed.
Further, in recent years, by using significantly advanced three-dimensional fluid simulation technology, flow conditions of the refrigerant and the lubricating oil in the hermetic container of the compressor can be visualized. Thus, new findings are obtained. Specifically, in Patent Literature 3, there is disclosed a refrigerant compressor in which an increase in head pressure that is generated near a leading end in a rotation direction of an upper balance weight at an upper end of the rotator of the electric motor arranged in the hermetic container is used to form an oil return passage from a vicinity of a leading end portion toward a lower end so that high density lubricating oil that appears around the rotator is returned below the electric motor, to thereby prevent the oil from flowing out.